As a UX designer, this is a failure of the UX designers, IMO. If you're a UX designer for web, you should be aware of web technology and be thinking about these things. Even if you don't know enough to fully specify it, you should be able to enough such that you can have conversations with a developer to work together to fully spec it out.

That said, I've also worked with some developers that didn't like intruding on their turf, so to speak. Though I've also worked with others that were more than happy to collaborate and very proactive about these sorts of things.

Furthermore, as a UX designer this is the sort of topic that we're unlikely to be able to meaningfully discuss with PMs and other stakeholders as it's completely non-visual and often trying to bring this up with them and discuss it ends up feeling like pulling teeth and them wondering why we're even spending time on it. So usually it just ended up being a discussion between me and the developers with no PM oversight.